<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        var arr ="      hello         ";
        var reg = /^\s+|\s+$/g;

        // 正则表达式
        console.log(arr.replace(reg,"$"));

        // trim方式
        console.log(arr.trim());
    </script>
</body>
</html>